1. Field of the Invention
The present invention relates generally to acoustic horns for loudspeakers and to methods of making such horns, and more particularly, to a cast acoustic horn for a loudspeaker having enhanced vibration damping characteristics.
2. Description of Related Art
A loudspeaker is a transducer which takes electrical energy and converts it into acoustic energy or sound. It includes a drive unit which converts the electrical signal into acoustic energy and a directional flare which directs the acoustic energy.
High quality reproduction of sound for speech and music requires the use of pressure drive units, known in the art as compression drivers. The compression drivers are at high levels coupled to a horn flare.
Traditionally, horn flares have been cast from rigid materials, such as metals and metal alloys. The use of a metal or metal alloy, such as aluminum, for fabricating the horn flare provides good mechanical strength, reduces the need for any additional bracing in the enclosure of the horn flare and also serves as a heat sink to provide additional cooling for the drive unit.
Casting horn flares from metals and metal alloys provides a horn flare that is economical to produce. However, the bell-like shape of such horn flares and the metallic materials produce a structure which suffers from severe structural resonances. These structural resonances are excited by vibration of the compression driver and cause a characteristic ringing sound which interferes with the quality of the sound produced by the loudspeaker.
Damping this sort of structural vibration is difficult. Prior methods have required large quantities of damping material. Other prior methods alternatively provide a thin film of damping material trapped between the horn and an additional structural member located between the horn and compression driver. However, in these prior damping methods, structural vibrations of the horn flare are not always satisfactorily damped and desired performance and costs objectives, among several other factors are often compromised.
In an attempt to reduce the structural resonances, and thus the characteristic ringing sound, plastic materials have been used as an alternative to metal for making the loudspeaker horn. However, a disadvantage of plastic materials is that these materials require additional support of a rear portion of the horn flare, lack the strength of metals, and do not provide a good heat sink for cooling of the drive unit.
The heat sink effect of the horn flare is best implemented by machining the flange of the horn to a flat shape, and replacing a foamed plastic gasket with a very thin film comprising thermally conductive materials. However, eliminating the foam gasket causes the vibrational damping on the horn to be reduced.